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water management

  • Cheaper to Remove Rather than Repair Dams, Study Finds

    A study that was recently conducted by researchers from Portland State University has found that removing aging dams across the country instead of repairing them could save billions of dollars, but cautions that more research is needed surrounding the factors that are driving efforts to remove dams across the country.

    The study, which was recently published online in the scientific journal River Research and Applications, assessed currently available nation-wide data on dams and compared characteristics and trends of dams which have been demolished to those which have been left standing.

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    If the current trend in dam demolition continues, the researchers estimate that anywhere between 4,000 - 36,000 dams will have been demolished by 2050.

    According to the study, the maximum cost of demolishing 36,000 dams is estimated to be around US$25.1 billion, which is significantly cheaper than the estimated cost of repairing these dams.

    According to estimates proposed by The American Society of Civil Engineers, it will cost more than US$45 billion to upgrade and repair around 2,170 dams considered high-risk to life and property should they fail. However, the cost of rehabilitating all the derelict dams in the US to bring them up to a condition deemed safe is higher still, estimated to be around US$64 billion.

    "I think it's time for a re-invigorated public process around managing the risks dams and aging dam infrastructure pose to public safety throughout the U.S.," said Zbigniew Grabowski, a Ph.D. candidate in PSU College of Liberal Arts and Science's Earth, Environment & Society program and lead author author of the study. "It's difficult to assess the actual public safety hazards and the most cost-effective ways of mitigating those hazards because the data on dams and dam removals has not been systematically compiled in a way that allows for robust analysis by government agencies or independent researchers."

    The researchers found that a disproportionately higher number of hydropower and water-supply dams were removed, suggesting more discussion is needed over the factors that drive dam removal.


    According to Grabowski, the decision to remove or rehabilitate a dam often hinges on cost-benefit tradeoffs between the environmental, social and economic impact of the dam in question. But, he says that we should also focus on public safety when making these decisions, as from a safety perspective it simply may not make sense to repair many of these dams.

    The study suggests several recommendations to improve the decision-making process, including:

    1.  Data collection methods used to track records of dams that are rehabilitated or removed need to be standardized and made available to the public to allow researchers to undertake more effective comparative research and for decision-makers at local, state and national levels to be able to make more informed management decisions.

    2.  Researchers and officials responsible for dam policy need to look at the broader picture when making decisions regarding the future of dams by taking a multi-disciplinary approach that draws knowledge from disciplines such as ecological restoration, dam safety engineering, technology and social science, while also considering communities that are affected by the presence or removal of dams.

    Journal Reference

    1. Zbigniew J. Grabowski, Heejun Chang, Elise L. Granek. Fracturing dams, fractured data: Empirical trends and characteristics of existing and removed dams in the United States. River Research and Applications, 2018; DOI: 10.1002/rra.3283

  • Beavers Dam Good at Cleaning Water

    Beavers dam building antics can help keep rivers clean and reduce the amount of valuable soil that is lost from farms with runoff, a new study has revealed.

    For the study, scientists from the University of Exeter analyzed the impact a family of captive beavers had on cleaning up a river. The beavers where confined in a 2.5 hectare enclosure on a stretch of river and used in a trial river cleanup coordinated by the Devon Wildlife Trust. The study demonstrates that the beavers significantly reduced the flow of nutrients and soil from nearby farmland into the river system. Just a single beaver family removed significant levels of nitrogen, phosphorus and sediment from water as it flowed through enclosure.


    The beaver family have been living within the fenced off site on a West Devon river since 2011, have constructed 13 dams which has stemmed the flow of water, creating several deep ponds along what used to be a shallow stream.

    The scientists measured the nitrogen, phosphorus and suspended sediment levels in the water as it flowed into the site, and again as it flowed out after passing through the beaver's dams and ponds. They then compared the before and after measurements, and also measured how much nitrogen, phosphorus and sediment was trapped by the beavers dams in each pond.

    They found that the beaver's dams had trapped more than 100 tonnes of sediment, of which 70% consisted of soil originating from intensively farmed grassland fields further upstream. They found that the trapped sediment contained high levels of nutrients (nitrogen and phosphorus) that pose both an environmental and health threat in high concentrations.

    "It is of serious concern that we observe such high rates of soil loss from agricultural land, which are well in excess of soil formation rates," said Professor Brazier. " However, we are heartened to discover that beaver dams can go a long way to mitigate this soil loss and also trap pollutants which lead to the degradation of our water bodies. Were beaver dams to be commonplace in the landscape we would no doubt see these effects delivering multiple benefits across whole ecosystems, as they do elsewhere around the world."

    A 2009 study estimated that soil loss from agricultural land in the United Kingdom equated to a financial cost of forty five million pounds, largely due to the negative impacts of nutrient and sediment pollution further downstream. Clearly beavers can play are positive role in keeping our waterways clean and healthy.

    The Devon Wildlife Trust has been running beaver trials in fenced off enclosures on local rivers for seven years, and in 2015 also began running a similar project using a wild population of beavers living on River Otter in East Devon.

    According to Peter Burgess, Director of Conservation and Development at the Devon Wildlife Trust, their partnership with the researchers from Exeter University is shedding light on the important contribution beavers can make in keeping freshwater systems healthy and sustainable for the benefit of both wildlife and humans. He finds it 'truly inspiring' to have their observations confirmed by robust scientific research.

    Journal Reference

    Alan Puttock, Hugh A. Graham, Donna Carless, Richard E. Brazier. Sediment and Nutrient Storage in a Beaver Engineered Wetland. Earth Surface Processes and Landforms, 2018; DOI: 10.1002/esp.4398

  • It's Time to Re-evaluate How we Value Water

    A new study led by researchers from the University of Oxford highlights the rapidly mounting pressure to measure, monitor and manage water on both a local and global scale, and proposes a new four-tiered approach to valuing water to ensure sustainable development and to help improve policy and water usage.

    Water is recognized as a valuable and vital resource for people and cultures, as well as industry, agriculture and the environment. Having access to safe drinking water is essential for human survival and for the long term survival of civilizations. This is reflected in the huge global financial investments in water treatment and sanitation, which is estimated to be approximately US$114 billion annually in capital expenditure alone.


    However, there is a growing need to re-assess the value of water. Not only is water essential for sustaining all forms of life on Earth, it also plays a key role in ensuring sustainable development. For example, all 17 of the United Nation's Sustainable Development Goals recognize the importance of water in achieving the sustainability objectives. These include developing sustainable cities, achieving peace and justice, and alleviating poverty and world hunger.

    Yet, global water security is increasingly becoming an area of growing concern. Droughts, floods and pollution all have a negative impact on water resources and communities. The World Economic Forum has listed water related threats within the top five global risks for a number of years now. A 2015 water security study conducted by Oxford researchers estimated costs associated with flooding, inadequate water supply, water shortages and poor sanitation to be around US$500 billion annually. The World Bank recently highlighted the economic and social impact of water scarcity, demonstrating that a drought costs a city four times as much as a flood event, while in rural Africa, a just one drought can trigger a downward spiral resulting in ongoing poverty and deprivation across generations.

    As economists, scientists and humanitarian aid groups recognize these trends, it is time for us to re-assess the value of water globally. Recognizing that the value of water extends far beyond the monetary value, the UN/World Bank High Level Panel on Water recently launched the Valuing Water initiative, which aims to guide policy and investment decision-making and encourage better governance in terms of managing water resources.

    The paper, which was recently published in Science, outlines a framework that places a value on water according to the Sustainable Development Goals rather than simply placing a monetary value on water or recognizing the cultural benefits of this precious natural resource. To this end, they recommend that water should be valued and managed through a four-prong approach that simultaneously highlights the need for measurement, valuation, trade-offs and capable institutions for allocating and financing water.

    "Our paper responds to a global call to action: the cascading negative impacts of scarcity, shocks and inadequate water services underscore the need to value water better", said Dustin Garrick, a researcher at Oxford University's Smith School of Enterprise and the Environment, who is the lead author of the paper. "There may not be any silver bullets, but there are clear steps to take. We argue that valuing water is fundamentally about navigating trade-offs. The objective of our research is to show why we need to rethink the value of water, and how to go about it, by leveraging technology, science and incentives to punch through stubborn governance barriers. Valuing water requires that we value institutions."

    According to Richard Damania, Global Lead Economist with the World Bank Water Practice and co-author of the paper, the study shows that water is key to development and therefore it is a resource that needs to be managed sustainably. He points out that multiple water management policies will be required in order to achieve multiple goals, and that current policies are outdated and inadequate for meeting current and future water related challenges.

    "Without policies to allocate finite supplies of water more efficiently, control the burgeoning demand for water and reduce wastage, water stress will intensify where water is already scarce and spread to regions of the world - with impacts on economic growth and the development of water-stressed nations," Damania warned.

    Earlier this month the University of Oxford hosted a one day forum, Valuing Water for Sustainable Development, where new approaches to how water is valued, financed and allocated were discussed. Conference presentations focused on several aspects of water management, including:

    1. Challenges to placing a value on water
    2. New tools to address these challenges
    3. Financial solutions to improve water infrastructure globally
    4. Making use of water markets to address water scarcity and shocks

    Oxford's Smith School of Enterprise and Research have released several video interviews with researchers who made presentations at the conference, which can be viewed here.

    Journal Reference

    Garrick, D.E., Hall, J.W., Dobson, A., Damania, R., Grafton, R.Q., Hope, R., Hepburn, C., Bark, R., Boltz, F., De Stefano, L., O'Donnell, E., Matthews, N. and Money, A. (2017) Valuing Water for Sustainable Development. Science. Vol 358. Issue 6366

  • Improve Water Quality by Installing Permeable Paving & Pervious Driveways

    In your efforts to make your home greener and more eco-friendly, you may want to consider doing your bit for water conservation by installing permeable paving and/or a pervious driveway. Pervious paving not only offers environmental benefits, it is also attractive, durable, requires very little maintenance, and doesn't cost too much to install. These characteristics alone make pervious driveways an investment worth considering, yet it has even more benefits to offer.

    Surface Water & Storm Water Management

    A key feature of pervious driveways is that they are constructed from permeable materials that allow rainwater to seep into the ground rather than wash away as surface runoff. This natural irrigation benefits the soil by reducing erosion and increasing soil moisture content, and replenishes groundwater systems which would otherwise not benefit fully from the rainfall.

    Illustration of relationship between impervious surfaces and surface runoff Illustration of relationship between impervious surfaces and surface runoff

    Since pervious paving is porous, water runoff is captured and absorbed into the ground, preventing storm-water runoff from overloading storm-water drains and sewer systems, thus reducing the risk of flooding.

    800px-Rasenpflasterstein_1 An example of a permeable driveway

    Surface runoff can potentially wash toxic contaminants, such as fertilizers, pesticides, oil and industrial chemicals off paved surfaces into streams, rivers and lakes, where it can endanger wildlife and contaminate drinking water resources. Because soil acts as a natural filter that removes contaminants from the water as it seeps through, by allowing water to soak into soil rather than washing into storm-water drains you can help keep our groundwater resources free from pollutants.

    Save Water by Reducing the Need for Irrigation

    By facilitating absorption or rainwater and snowmelt into the soil you will minimize the need to irrigate your garden, lawn and surrounding landscape. This not only saves water, but will save you money on your water bill too.

    Reducing the Heat Island Effect

    A common problem associated with hard surfaces, such as concrete and asphalt, is that they absorb heat from the sun, which accumulates, resulting in high ambient temperatures in urban environments – a phenomenon known as the 'heat island effect'.

    Pervious paving allows water to filter through the soil into the ground, helping it to stay damp and cool. This provides a natural cooling effect to the surrounding area, which is enhanced if light colored materials are used that reflect heat away. Both surface and surrounding air temperatures are cooler compared to when hard impervious materials are used on driveway surfaces. These cool, damp conditions also stimulate growth and promote vigor of local plants.

    Benefits in Cold Climates

    In areas that have colder climates pervious paving provides extremely good traction when walking on the surface, which may prevent injuries from slips and falls associated with slippery surfaces. When ice begins to melt the meltwater seeps into the ground preventing it from refreezing to create potentially hazardous conditions.

    Enhanced Appearance

    Pervious paving typically has more aesthetic appeal than standard concrete or asphalt, which tends to be rather monotonous. There are many options to choose from, including:

    • Pervious concrete – a porous type of concrete that consists of stone aggregate and cement, but very little sand, resulting in a porous cement that contains many drainage holes within the surface to allow water to drain away.

    • Open-cell concrete blocks or permeable pavers – these paving blocks are specifically designed to take the weight of vehicles yet allow water to drain away into the soil below. Spaces in the blocks can be filled with sand or gravel, or grass or other ground cover can be grown in the spaces between blocks to eliminate heat buildup.

    So, if you are looking for simple ideas to green up your property, a pervious driveway or paving system offers a fantastic solution to prevent stormwater runoff, save water, minimize costs, and at the same time improve the aesthetics and value of your property.

  • Can Your Drinking Water Get Hacked?

    Cyber attacks are a growing concern, that could potentially affect both commercial and governmental enterprises globally. Now government officials are cautioning water utilities to focus more attention on this rising threat.

    With more and more water utilities trying to cut down on their operating expenses by opting for fully automated systems, the threat is likely to increase in the years to come, BNA Bloomberg reports.

    The US Environmental Protection Agency (EPA) together with input from the Dept of Homeland Security (DHS) are busy developing training manuals to help smaller, rural water systems that lack the necessary resources to defend themselves against threat posed by cyber hackers.


    According to Helen Jackson from the DHS's Office of Cybersecurity and Communications, these threats to water distribution networks can come in various guises. For example, one type of threat is ransomeware — where computer hackers hijack and take control of computer controlled equipment and demand payment of a ransom to give back control of the equipment. Insider threats — where a computer system is compromised by someone who has access to the utility — is another. According to Jackson, a 2015 survey conducted by computer giant IBM revealed that more than 50% of all cyber security incidents in the corporate world involved insider threats.

    Once hackers gain access to a water utility's computer system, they have the ability to control factors such as chlorine flow rates as well as ratios of other chemical additives added to drinking water during the treatment process.

    YouTube Video:

    David Travers, director of water security at the EPA, feels that as water utilities become more automated they are becoming increasingly vulnerable to cyber threats and need to be more vigilant to protect themselves from potential hackers.

    "As we rely on a fully automated system, I think there's a certain degree of expertise that's lost", said Travers. "Now you have operators who may not know how to run the system" in the event of an outage.

    Travers urges water utilities to prepare for cyber threats by running hands-on tabletop simulation exercises that would increase the capacity of technicians to handle any such threat. Jackson echoes his sentiments, pointing to industry resources that can help utilities assess their cyber security risk.

    Water distribution networks have faced cyber security attacks before. More than 10 years ago in 2006, a computer hacker gained access to the computer system at a water filtration plant located near Harrisburg, PA, and attempted to use the computers network to distribute pirated software and emails. Upon investigation the FBI found that the computer in question controlled a vital system of the water plant and had the attack caused it to malfunction, service to consumers would have been disrupted. Then 10 years later, in 2016, hackers gained access to a water treatment plant and were able to manipulate chlorine levels.

    In this day and age, cyber security is a real threat, and needs to be taken seriously by water utilities. Should the security of your local water utility be breached, do you have a contingency plan to ensure you have access to safe drinking water?

  • Managing Animal Waste to Prevent Water Contamination

    Water quality in our streams, rivers and dams is not only important so that people can enjoy the recreational opportunities these freshwater bodies offer, it is also essential for healthy food production as well as clean drinking water.

    Contaminants originating from animal waste are a potential source of contamination to our freshwater systems. These include nutrients such as nitrates, and to a lesser extent, veterinary drugs and hormones used in animal husbandry. But, no matter whether you are farmer who manages a large agricultural enterprise, a smallholder who keeps a few farm animals, or a homeowner with a vast menagerie or even just a few domestic pets, you can implement measures to prevent contamination of local water sources.


    As the agricultural sector is considered a potential source of freshwater contaminants, these operations are now regulated, with certain rules imposed for managing animal feeding lots to ensure animal manure is collected and managed appropriately.

    Yet, while large livestock operations are an obvious source of potential contamination, the reality is that any property where animals (livestock or domestic pets) are kept is a potential source of water contamination. The size of the operation is not necessarily a good barometer of its impact, as smaller operations that are not managed properly can have a bigger impact than larger operations where manure is well managed. Therefore, it is clear that anyone who raises or keeps animals on their property can play an important role in preventing contamination of our water resources if they implement a suitable animal waste management program.

    Animal waste management is by no means a new concept in the agricultural sector. Farm managers have been collecting manure produced by their livestock and utilizing this byproduct as a fertilizer for decades, if not centuries. Manure is high in nutrients that can improve the quality of soils, and are beneficial for growing crops, improving crop yields. Consequently, many smallholders also utilize manure as a valuable fertilizer to grow crops.

    However, when manure is not properly managed, these nutrients can leach through soils into groundwater or wash into surface waters with runoff, where they can accumulate, becoming more concentrated over time. This results in nutrient loading, which can lead to algal blooms and eventually lowered oxygen levels in freshwater bodies. Nitrates in high concentrations are also a drinking water contaminant that can have grave health impacts, particularly on infants and pregnant women, and has also been linked to several types of cancer.

    It is therefore essential that everyone who keeps animals develops a sound manure management plan. This will not only prevent unwanted water contamination, but can also result in more efficient farming operations. To be successful, an animal waste management plan needs to address the issues of manure generation, storage and disposal on the farm. First, you need to estimate how much manure is generated on your farm. Then you need to decide whether you are going to store the manure on site for composting, or send it off site for composting or disposal. One common method of disposal is to spread it over croplands. But if this method is used, it is best to determine the nutrient requirements of your crop and spread the manure accordingly. Also, bear in mind that the nutrients present in manure are not all available to the plants immediately. So, when using manure as a nutrient source it should be viewed as part of the overall nutrient cycling that takes place on the property, serving as a valuable soil enhancer when used appropriately.

    Homeowners can also do their bit by managing the animal waste produced on their property, and following appropriate practices when fertilizing their gardens and lawns to minimize nutrient runoff. Regardless of whether you are a farmer, smallholder or homeowner, you can implement small measures to help improve water quality in your watershed, making the water safer for your community.

  • Muddy Waters: Climate Change Could Lead to Murkier Lakes

    An assessment of over 5000 lakes in Wisconsin revealed that nearly 25% of them have gotten more murky over the last twenty years. The study also indicates that things could get worse as a result of increased precipitation due to climate change.

    The study, which was conducted by scientists from the University of Wisconsin-Madison in collaboration with the Wisconsin Department of Natural Resources, also suggests measures that can be taken to improve water quality, such as increasing the riparian buffer zone by restricting agriculture on land immediately bordering Wisconsin's rivers and lakes, which would limit nutrient runoff and thus improve the clarity of the water.

    "In the face of increasing precipitation, this analysis provides empirical support for the fact that adapting our landscape is going to be important into the future," says co-author Monica Turner, a UW-Madison professor of zoology.

    The authors suggest farming should be limited to within 10% of the riparian buffer zone surrounding lakes and rivers or streams that flow into those lakes. Leaving natural vegetation on the banks of rivers and lakes would reduce nutrient and sediment runoff during heavy rains, and would also benefit farmers who often suffer extensive damages to crops when rivers rise.


    While the study shows that water clarity has remained unchanged for most of the lakes studied, with 6% actually showing an improvement in water clarity, the number of lakes where water clarity is getting worse is concerning, and indicates that preventative action needs to be taken to maintain water quality.

    "If we want to maintain or improve water clarity, we need to think about trends in precipitation," says lead author Kevin Rose, formerly a postdoctoral researcher at UW-Madison and now an assistant professor of freshwater ecology at Rensselaer Polytechnic Institute in New York.

    The studies findings, which were recently published in the scientific journal Ecological Applications, shows that water clarity in lakes that generally have clear water deteriorates during wetter years. Lakes with good water clarity tend to be more vulnerable to the torrent of nutrients and debris that flows in after heavy rainfall, which can result in the water turning murky or brown due to the increased sediment and debris, or even green due to an increase in algal growth fueled by excessive nutrients.

    According to Turner, the study's results provide concrete evidence of what computer models predict, reflecting that water clarity in Wisconsin Lakes could decline as precipitation increases in the future unless measures are taken to improve landscape management, particularly in riparian buffer zones.

    The study highlights the need to look ahead so that we can anticipate how changes to the landscape and climate may affect our lakes, Turner explains, which will in turn allow us to implement measures to protect both Wisconsin's lakes and farmers.

    "It absolutely provides evidence for the importance of continuing to look for solutions to sustain the economy of Wisconsin without sacrificing the quality of our water," she says.

    Journal Reference

    Kevin C Rose, Steven R. Greb, Matthew Diebel, Monica G. Turner. Annual precipitation regulates spatial and temporal drivers of lake water clarity. Ecological Applications, 2016; DOI: 10.1002/eap.1471

  • Using Sound to Echolocate Underground Water Leaks

    Researchers from Concordia University have developed a method of locating underground in distribution networks with a 99.5% accuracy.

    Water scarcity is a worldwide problem that will challenge 33% of the global population by 2025. This water crisis can be averted if one of the main culprits — leaks — can be addressed. It is estimated that between 20-30% of water leaving water treatment plants is lost as a result of water leakage, which can be resolved if the problem is addressed and fixed.

    water-pipe-880975_960_720 (1)

    But first we have to find the leaks, which can be difficult to detect when pipes are buried underground. When repair work is undertaken, this needs to be done as precisely as possible, to not only limit the cost involved with excavation work and resurfacing, but also to limit disruptions to traffic, commuter frustration, and loss of income due to disruptions to local trade and industry.

    Furthermore, leaking pipes not only waste valuable water; damaged water pipes allow pollutants to enter the water flowing through them via the holes in the pipelines, posing a drinking water hazard and health risk to consumers.

    Thankfully, scientists from Concordia University, Montreal, have developed an innovative tool — known as a noise logger — to address this problem. They recently conducted a study to test the effectiveness of the tool, traveling to Doha in the water scarce nation of Qatar to apply the noise logger in detecting water leaks within Qatar University's water network.
    Qatar not only has one of the lowest rainfall rates globally, but also among the highest evaporation rates globally. Consequently, when rain does fall it quickly evaporates back into the atmosphere in the form of water vapor.

    According to co-author, Tarek Zayed, a professor in the Department of Building, Civil and Environmental Engineering at Concordia University: "Qatar is currently facing significant challenges regarding its water supply. Its water distribution network currently suffers from 30-35% water loss due to leakage."

    The results of the study, which where recently published in the Journal of Infrustructure, show that the noise logger is not only effective at detecting leaks, but can do so with fine accuracy before any major earthworks are required.

    "This approach can reduce the duration of a leak, as well as the cost and time involved in locating the site in need of repair." " explains Zayed

    To test their theory, the researchers installed noise loggers on Qatar University's water mains network to record sounds generated by water leaks over a 2-hour period. They then scrutinized the sound readings, comparing noise level and spread. The researchers deemed a leak investigation necessary when a consistent sound anomaly was detected.

    After monitoring Qatar University's water mains for several weeks they collected sound readings from 140 points across the water network. They then used mathematical model simulations to pin-point the exact location of where water leaks were occurring. After investigating the locations of the leaks, Qatar University's facilities management reported that the researchers had detected the leaks with 99.5% accuracy.

    The researchers now plan to conduct surveys of leak data from real-life municipal water networks where noise loggers are used in an effort to develop tailor-made leak location prediction models.

    Journal Reference
    El-Abbasy, M., Mosleh, F., Senouci, A., Zayed, T., and Al-Derham, H. (2016). "Locating Leaks in Water Mains Using Noise Loggers." J. Infrastruct. Syst. , 10.1061/(ASCE)IS.1943-555X.0000305 , 04016012.

  • Watershed Biogeochemistry is Influenced by Stormy Weather

    A new study led by researchers from Yale University suggests that severe storm events cause excessive amounts of organic matter to circumvent headwater systems, resulting in this material being pushed downstream where it flows into larger rivers, inland basins and coastal waters, having profound effects on water quality throughout the watershed.

    The study, which was recently published in the scientific journal Ecology, has found that this phenomenon not only affects water quality, but also the ecology and chemical processes that take place within these ecosystems. Dissolved organic material — which consists of a mixture of various compounds that leach into freshwater systems that gives streams and rivers their color — is also a source of nutrients and contaminants, and it has a large influence on light penetration into the water and the release of carbon dioxide from the water, which consequently affects abundance of phytoplankton — primary producers at the bottom of aquatic food chains that are directly and indirectly a key food source for a wide range of organisms.


    Until now, scientists have believed that organic matter is naturally processed in the upper stretches close to its origins, broken down by freshwater organisms dwelling in these headwaters into new compounds, which are then carried downstream and processed by organisms living further downstream, with a similar process occurring right throughout the freshwater system — a process that scientists refer to as the "River Continuum Concept".

    However, this new study highlights the fact that this process doesn't take heavy storm events into account, which send "pulses" of organic material into waterways. Not only are large amounts of debris pushed downstream during these events, because the flow rate is much faster during heavy storm events, they are pushed beyond the headwaters before the above reactions have had time to take place — a theory referred to as the "pulse-shunt concept."

    "We predict that a lot of this organic matter is actually shunted past the small streams and the reactions occur in the larger rivers or even in the coastal ocean," said lead author, Peter Raymond, a professor of ecosystem ecology at the Yale School of Forestry & Environmental Studies (F&ES). "We also offer a new conceptual theory for watershed biogeochemistry that demonstrates this through first principles and is transferable to other watersheds and other nutrients."

    Previous studies estimated that around 60% of organic matter originating from terrestrial sources occurs over 15 days, including days where heavy rainfall or snow melt occurred.
    According to Raymond, even though heavy weather occurs infrequently, more organic matter is transported from the landscape during heavy storm events than in smaller events, as the concentration of the material increases in relation to the size of the event. However, he points out that the 'shunt', or flow rate, during these more severe events results in more material flowing downstream as there is insufficient time for it to be processed by organisms further upstream. As a result, we see a "double additive effect" where more of this organic material is exported to coastal waters," explains Raymond.

    According to the authors, these shifts in the transportation of dissolved organic matter could potentially affect water clarity, dissolved oxygen concentrations, and could also be a source of mercury to inland freshwater systems.

    This clearly has implications for drinking water quality too. While turbidity and dissolved solids can affect the appearance of drinking water, making it unpleasant to drink, the suspended organic matter can also harbor contaminants such as mercury, making it unsafe to drink.

    Journal Reference

    PA Raymond, JE Saiers & WV Sobczak. Hydrological and biogeochemical controls on watershed dissolved organic matter transport: pulse-shunt concept. Ecology. Vol 97(1). Jan 2016; DOI: 10.1890/14-1684

  • Rethinking Watershed Management

    A recently published analysis of how land cover and climate change will affect watersheds across the United States, provides options for the management of runoff, storm water and floods that can be implemented by decision-makers to manage water quality.

    The study, which was recently published in the Journal of Geophysical Research Biogeosciences, was conducted by scientists from the University of Massachusetts Amherst, who hope that the models and simulations produced will provide managers with practical ways to encourage land developers to implement water quality and conservation measures and to incorporate green infrastructure into their projects.


    Using data collected from satellite images, field stations, temperature gauges, stream gauges and water flow observations across the United States, the study connects the dots between land use and climate (notably temperature and rainfall/precipitation) to runoff and flooding within a watershed drainage system at a much larger scale than ever before.

    According to co-author, Timothy Randhir, of the Department of Environmental Conservation at the University of Massachusetts Amherst, this new information will give us a clearer understanding of the mechanisms and runoff processes in large watersheds.

    “We also want to highlight the importance of natural systems such as forest cover and open space when a town is considering new parking lots or shopping centers, for example. You can't just take away such ecosystem services and expect everything to be OK,” said Randhir. “All towns now have a big problem dealing with storm water, and with climate change it's going to get worse. In the past, the problems just flowed away to become some other town's problem, but that isn't going to work anymore.”

    Randhir hopes that this will encourage a new approach to the way managers manage water resources, moving away from the current reactive approach, where managers deal with stormwater and runoff issues after they have become problematic, to a more active approach where they take preventative measures before problems arise.

    “There seems to be a better understanding now that water flowing away from you doesn't just disappear, it affects someone else, and a problem in the system above you will affect you,” said Randhir. “This kind of systems thinking has to take over, and cooperation has to be used more often.”

    The report suggests recommendations on how to utilize tools such as improving infiltration or urban greening as mitigation measures to reduce flooding. According to Randhir, by combining green infrastructure with best management practices watersheds can made more resilient. It is in a town or city’s own best interests to encourage these measures by offering incentives to developers who install pervious surfaces that promote rainwater infiltration rather than impervious concrete that promote stormwater runoff; or water retention features such as drainage basins or rain gardens that capture runoff that is contaminated with heavy metals, grease and oil washed off road surfaces as well as sediments from soil surfaces.

    Land managers can also introduce incentives to farmers and private landowners to encourage them to take measures to prevent runoff on their properties. Randhir hopes that town and city managers make use of this new information to initiate changes to their land use practices. By doing so, flooding will be reduced, and water quality will improve for users downstream.

    Journal Reference

    Paul Ekness, Timothy O. Randhir. Effect of climate and land cover changes on watershed runoff: A multivariate assessment for storm water management. Journal of Geophysical Research: Biogeosciences, 2015; DOI: 10.1002/2015JG002981

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